1. Field of the Invention
This invention relates to a foamed, low density, highly extended, polymerized unsaturated polyester resin syrup product and to an unpolymerized composition mixture which cures to a foamed product. This invention also relates to a shaped article comprised of the foamed, low density, highly extended, polymerized unsaturated polyester resin syrup composition and to a process of preparing a shaped article.
2. Description of the Prior Art
It is known in the art that foamed polymeric products may be prepared by incorporating a compound which generates a blowing agent in situ. Thus, for example, U.S. Pat. No. 3,224,983 describes the use of organic carbonates which, when heated, liberate carbon dioxide as a blowing agent for various thermoplastic resins. The temperature at which the carbon dioxide is liberated can be lowered by an activator which may be certain inorganic acids, bases or salts exemplified by sodium carbonate and sodium bicarbonate. Similarly, U.S. Pat. No. 3,470,114 discloses the preparation of foamed saturated polyesters wherein carbon dioxide is generated from an aromatic polycarbonate.
Foamed unsaturated polyester resin syrup products are described in U.S. Pat. No. 3,884,844. To obtain such products, the reaction is conducted under subatmospheric pressure at a range of about 180 to 50 Torr, in the presence of a volatile blowing agent and a nucleating agent. The blowing agent can be any compound which will release gas under the reaction conditions. The patent further states that dispersing agents, surfactants, cell stabilizers, flame retardants, fillers and reinforcing agents may be optionally added to the compositions.
U.S. Pat. No. 4,028,289 relates to a stabilized polyester resin product which is foamed using bicarbonate of soda. The product also contains an inorganic filler in amount ranging up to 80% or more of the weight of the polyester-filler material.
Other patents which disclose a variety of foamed unsaturated polyester resin products include U.S. Pat. Nos. 3,920,589, 4,016,112, 4,028,289, 4,119,583. However, all such known foamed polyester resin products have failed to provide high extension with attendant excellent strength and fire properties. This is due to the large increase in viscosity which typically accompanies the addition of filler material to polyester compositions and which makes handling by conventional apparatus impossible.
In applicant's U.S. Pat. No. 4,192,791, a non-foamed, high density, polymerized unsaturated polyester resin syrup product containing basic aluminum chloride is disclosed. Although high extensions may be obtained, the inherent high density of the composition (i.e., 115-120 lbs/cu ft) constitutes a disadvantage in certain environments. Additionally, unless certain precautions are taken, the composition exhibits a slight shrinkage in volume upon curing which must be considered when the precise dimensions of the shaped article are of importance.
Accordingly, the art has heretofore failed to provide a foamed, low density, highly extended polymerized unsaturated polyester resin syrup product which exhibits excellent strength, fire and insulative properties or a composition or a process whereby such products can be made.
For clarity, the following expressions are employed in this specification and claims.
Composition--refers to the starting ingredients and their relative proportions. The "composition" of this invention is a foamable composition.
Composition mixture--refers to a mixture in which all ingredients of the composition are mixed. The "composition mixture" of this invention is actively foaming.
Component--refers to mixtures of ingredients which are subsequently combined with other "components" to form the composition mixture.
Product--refers to the solid, foamed article which is obtained by the reactions of a composition mixture.